Compliant interconnect assembly

ABSTRACT

An apparatus and method for making a compliant interconnect assembly. The compliant interconnect assembly includes a first carrier having a first major surface and a plurality of through openings. A first major surface of a first flexible circuit member having a plurality of electrical traces is attached to the first major surface of the first carrier. The electrical traces include a plurality of compliant members having at least one distal end projecting in one of the openings of the first carrier. A first major surface of a second carrier is positioned opposite a second major surface of the first flexible circuit member. The second carrier has a plurality of through openings aligned with the plurality of the compliant members.

REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation-in-part application of U.S.patent application Serial No. 10/169,431 filed Jun. 26, 2002 entitled“Flexible Compliant Interconnect Assembly”, which claims priority toPCT/US01/00872 filed Jan. 11, 2001, which claims the benefit of U.S.provisional application serial No. 60/177,112 filed Jan. 20, 2000, allof which are hereby incorporated by reference.

FIELD OF THE INVENTION

[0002] The present invention is directed to a method and apparatus forachieving a compliant, solderless or soldered interconnect betweencircuit members.

BACKGROUND OF THE INVENTION

[0003] The current trend in connector design for those connectorsutilized in the computer field is to provide both high density and highreliability connectors between various circuit devices. High reliabilityfor such connections is essential due to potential system failure causedby misconnection of devices. Further, to assure effective repair,upgrade, testing and/or replacement of various components, such asconnectors, cards, chips, boards, and modules, it is highly desirablethat such connections be separable and reconnectable in the finalproduct.

[0004] Pin-type connectors soldered into plated through holes or viasare among the most commonly used in the industry today. Pins on theconnector body are inserted through plated holes or vias on a printedcircuit board and soldered in place using conventional means. Anotherconnector or a packaged semiconductor device is then inserted andretained by the connector body by mechanical interference or friction.The tin lead alloy solder and associated chemicals used throughout theprocess of soldering these connectors to the printed circuit board havecome under increased scrutiny due to their environmental impact.Additionally, the plastic housings of these connectors undergo asignificant amount of thermal activity during the soldering process,which stresses the component and threatens reliability.

[0005] The soldered contacts on the connector body are typically themeans of supporting the device being interfaced by the connector and aresubject to fatigue, stress deformation, solder bridging, andco-planarity errors, potentially causing premature failure or loss ofcontinuity. In particular, as the mating connector or semiconductordevice is inserted and removed from the present connector, the elasticlimit on the contacts soldered to the circuit board may be exceededcausing a loss of continuity. These connectors are typically notreliable for more than a few insertions and removals of devices. Thesedevices also have a relatively long electrical length that can degradesystem performance, especially for high frequency or low powercomponents. The pitch or separation between adjacent device leads thatcan be produced using these connectors is also limited due to the riskof shorting.

[0006] Another electrical interconnection method is known as wirebonding, which involves the mechanical or thermal compression of a softmetal wire, such as gold, from one circuit to another. Such bonding,however, does not lend itself readily to high-density connectionsbecause of possible wire breakage and accompanying mechanicaldifficulties in wire handling.

[0007] An alternate electrical interconnection technique involvesplacement of solder balls or the like between respective circuitelements. The solder is reflown to form the electrical interconnection.While this technique has proven successful in providing high-densityinterconnections for various structures, this technique does notfacilitate separation and subsequent reconnection of the circuitmembers.

[0008] An elastomeric material having a plurality of conductive pathshas also been used as an interconnection device. The conductive elementsembedded in the elastomeric sheet provide an electrical connectionbetween two opposing terminals brought into contact with the elastomericsheet. The elastomeric material must be compressed to achieve andmaintain an electrical connection, requiring a relatively high force percontact to achieve adequate electrical connection, exacerbatingnon-planarity between mating surfaces. Location of the conductiveelements is generally not controllable. Elastomeric connectors may alsoexhibit a relatively high electrical resistance through theinterconnection between the associated circuit elements. Theinterconnection with the circuit elements can be sensitive to dust,debris, oxidation, temperature fluctuations, vibration, and otherenvironmental elements that may adversely affect the connection.

[0009] The problems associated with connector design are multiplied whenmultiple integrated circuit devices are packaged together in functionalgroups. The traditional way is to solder the components to a printedcircuit board, flex circuit, or ceramic substrate in either a bare diesilicon integrated circuit form or packaged form. Multi-chip modules,ball grids, array packaging, and chip scale packaging have evolved toallow multiple integrated circuit devices to be interconnected in agroup.

[0010] One of the major issues regarding these technologies is thedifficulty in soldering the components, while ensuring that rejectconditions do not exist. Many of these devices rely on balls of solderattached to the underside of the integrated circuit device which is thenreflown to connect with surface mount pads of the printed circuit board,flex circuit, or ceramic substrate. In some circumstances, these jointsare generally not very reliable or easy to inspect for defects. Theprocess to remove and repair a damaged or defective device is costly andmany times results in unusable electronic components and damage to othercomponents in the functional group.

[0011] Many of the problems encountered with connecting integratedcircuit devices to larger circuit assemblies are compounded inmulti-chip modules. Multi-chip modules have had slow acceptance in theindustry due to the lack of large scale known good die for integratedcircuits that have been tested and burned-in at the silicon level. Thesedies are then mounted to a substrate, which interconnect severalcomponents. As the number of devices increases, the probability offailure increases dramatically. With the chance of one device failing insome way and effective means of repairing or replacing currentlyunavailable, yield rates have been low and the manufacturing costs high.

BRIEF SUMMARY OF THE INVENTION

[0012] The present invention is directed to a method and apparatus forachieving a fine pitch interconnect between circuit members. Theconnection with the circuit members can be soldered or solderless. Thecircuit members can be printed circuit boards, another flexible circuit,a bare-die device, an integrated circuit device, an organic or inorganicsubstrate, a rigid circuit and virtually any other type of electricalcomponent. The present invention is also directed to an electricalinterconnect assembly comprising one or more flexible circuit memberselectrically coupled to a plurality of circuit members.

[0013] In one embodiment, the compliant interconnect assembly includes afirst carrier having a first major surface and a plurality of throughopenings. A first major surface of a first flexible circuit memberhaving a plurality of electrical traces is attached to the first majorsurface of the first carrier. The electrical traces comprise a pluralityof compliant members having at least one distal end projecting in one ofthe openings of the first carrier. A first major surface of a secondcarrier is positioned opposite a second major surface of the firstflexible circuit member. The second carrier has a plurality of throughopenings aligned with the plurality of the compliant members. Thecarrier can be a rigid, semi-rigid or flexible material.

[0014] The distal ends are preferably deformed to project through anopening in the first carrier. In some embodiments, the distal end isdeformed to extend through an opening in the first carrier and to extendabove a second major surface of the first carrier. Each compliant membercan have one or more distal ends. For example, a single compliant membercan have a first distal end deformed to project in an opening in thefirst carrier and a second distal end deformed to project in an openingin the second carrier. It is also possible for solder balls to belocated in the openings in the second carrier and electrically coupledwith the compliant members.

[0015] A first circuit member having contact pads is aligned with, andelectrically coupled to, the distal ends of the compliant members. Thefirst circuit member can be a printed circuit board, a flexible circuit,a bare die device, an integrated circuit device, organic or inorganicsubstrates, or a rigid circuit. A second circuit member having contactpads is aligned with the holes in the second carrier. For example, thesecond circuit member is electrically coupled to the compliant membersthrough the holes in the second carrier using solder.

[0016] An additional circuitry plane can be attached to a second majorsurface of the second carrier. The additional circuitry plane includes aplurality of through openings aligned with the plurality of openings inthe second carrier. The additional circuitry plane can be one of aground plane, a power plane, or an electrical connection to othercircuit members. In another embodiment, one or more discrete electricalcomponents, such as capacitors, can be electrically coupled to the firstflexible circuit member.

[0017] In some embodiments a second flexible circuit member is attachedto the first major surface of the second carrier. The electrical tracesinclude a plurality of compliant members having at least one distal endprojecting in one of the openings of the second carrier. An electricalconnection is formed between the compliant members on the first flexiblecircuit member and the compliant members on the second flexible circuitmember. Optional dielectric layers can be located between the first andsecond flexible circuit members. The electrical connection can be formedusing solder, a conductive plug, compression, conductive adhesive, or avariety of other mechanisms. In another embodiment, the second carrieris attached to a printed circuit board and the compliant members areelectrically coupled to contact pads on the printed circuit boardthrough the openings in the second carrier.

[0018] In one embodiment, a portion of the first flexible circuit memberextends beyond the compliant interconnect assembly to permit electricalcoupling with another circuit member. A portion of the first flexiblecircuit member can extend beyond the compliant interconnect assembly toform a stacked configuration other compliant interconnect assemblies.

[0019] In another embodiment, the compliant interconnect assemblyincludes a first carrier having a first major surface and a plurality ofthrough openings. At least one discrete compliant member extends throughan opening in the first carrier and is attached to the first carrieradjacent to the openings. The compliant member has at least one distalend projecting away from the first carrier. A second carrier having afirst major surface is positioned opposite the first major surface ofthe first carrier. The second carrier has a plurality of openingsthrough which the distal ends of the compliant members extend.

[0020] The compliant interconnect assembly can include a plurality ofelectrical traces attached to the first major surface of the firstcarrier. The electrical traces comprises a plurality of compliantmembers having at least one distal end projecting in one of the openingsof the first carrier. The compliant members can have two distal endsprojecting away from opposite sides of the first carrier. Alternatively,solder balls can be electrically coupled to the compliant members so asto project away from a second major surface of the first carrier.

[0021] The present invention is also directed to a method of making acompliant interconnect assembly. A first major surface of a firstflexible circuit member is attached to the first major surface of thefirst carrier so that distal ends of compliant members project in one ofthe openings in the first carrier. The first flexible circuit member issingulated so that a portion of the compliant members are electricallyisolated from the electrical traces. A second carrier is positionedopposite a second major surface of the first flexible circuit member sothat the through openings in the second carrier are aligned withcompliant members.

[0022] In one embodiment, an additional circuitry plane is attached to asecond major surface of the second carrier. The additional circuitryplane comprises a plurality of through openings aligned with a pluralitythrough openings in the second carrier. The additional circuitry planecan be a ground plane, a power plane, or an electrical connection toother circuit members. Selected compliant members can be electricallycoupled to the additional circuitry plane. One or more discreteelectrical components, such as capacitors, can be attached to the firstflexible circuit member.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a substrate used for making a compliant interconnect inaccordance with the present invention.

[0024]FIG. 2 is a side sectional of the substrate of FIG. 1 with amasking material applied in accordance with the present invention.

[0025]FIG. 3 is a side sectional view of the substrate and maskingmaterial of FIG. 2 with an additional hole in accordance with thepresent invention.

[0026]FIG. 4 is a side sectional view of a compliant material applied tothe substrate of FIG. 3.

[0027]FIG. 3 is a side sectional view of a method of modifying theelectrical interconnect of FIG. 2.

[0028]FIG. 4 is a side sectional view of an electrical contact modifiedin accordance with the method of the present invention.

[0029]FIG. 5 is a side sectional view of a compliant interconnectassembly in accordance with the present invention.

[0030]FIG. 6 is a side sectional view of the compliant interconnectassembly of FIG. 5 in a compressed state in accordance with the presentinvention.

[0031] FIGS. 7-9 are side sectional views of an alternate compliantinterconnect in accordance with the present invention.

[0032]FIG. 10A is a perspective view of a flexible circuit member inaccordance with the present invention.

[0033]FIG. 10B is a perspective view of an alternate flexible circuitmember in accordance with the present invention.

[0034]FIG. 10C is a perspective view of another alternate flexiblecircuit member in accordance with the present invention.

[0035]FIG. 10D is a top view of electrical traces of a flexible circuitmember prior to singulation.

[0036]FIG. 10E is a top view of the flexible circuit member of FIG. 10Dafter singulation.

[0037]FIG. 10F is a top view of electrical traces of a flexible circuitmember prior to singulation.

[0038]FIG. 10G is a top view of electrical traces of a flexible circuitmember prior to singulation.

[0039]FIG. 10H is a top view of electrical traces of a flexible circuitmember prior to singulation.

[0040]FIG. 10I is a top view of electrical traces of a flexible circuitmember prior to singulation.

[0041]FIG. 11 is a side sectional view of a compliant interconnectassembly in accordance with the present invention.

[0042]FIG. 12A is a side sectional view of an alternate compliantinterconnect assembly in a stacked configuration in accordance with thepresent invention.

[0043]FIG. 12B is a side sectional view of an alternate compliantinterconnect assembly with a spring member in accordance with thepresent invention.

[0044]FIG. 12C is a side sectional view of an alternate compliantinterconnect assembly with a sheet of spring members in accordance withthe present invention.

[0045]FIG. 12D is a side sectional view of an alternate compliantinterconnect assembly using one of the flexible circuit members of FIGS.10D-10I.

[0046]FIG. 13 is a side sectional view of an alternate compliantinterconnect assembly with a carrier in accordance with the presentinvention.

[0047]FIG. 14A is a side sectional view of a compliant interconnectassembly on an integrated circuit device in accordance with the presentinvention.

[0048]FIG. 14B is a side sectional view of an alternate compliantinterconnect assembly on an integrated circuit device in accordance withthe present invention.

[0049]FIG. 15A is a side sectional view of a compliant interconnectassembly with a carrier and an integrated circuit device in accordancewith the present invention.

[0050]FIG. 15B is a side sectional view of a compliant interconnectassembly packaged with an integrated circuit device in accordance withthe present invention.

[0051]FIG. 16 is a replaceable chip module using the compliantinterconnect assembly in accordance with the present invention.

[0052]FIG. 17 is a side sectional view of a plurality of compliantinterconnect assemblies in a stacked configuration in accordance withthe present invention.

[0053]FIG. 18 is a top view of a compliant interconnect assembly withthe flexible circuit members extending therefrom in accordance with thepresent invention.

[0054]FIG. 19 is a side sectional view of a plurality of circuit membersin a stacked configuration coupled using a compliant interconnectassembly in accordance with the present invention.

[0055]FIG. 20 is a side sectional view of various structures on aflexible circuit member for electrically coupling with a circuit member.

[0056]FIG. 21 is a side sectional view of an alternate compliantinterconnect assembly using one of the flexible circuit members of FIGS.10D-10I.

[0057]FIG. 22 is a side sectional view of an alternate compliantinterconnect assembly using one of the flexible circuit members of FIGS.10F-10I.

[0058]FIG. 23 is a side sectional view of an alternate compliantinterconnect assembly using a pair of the flexible circuit members, suchas illustrated in FIGS. 10D-10I, in a back to back configuration.

[0059]FIG. 24 is a side sectional view of an alternate compliantinterconnect assembly using a pair of the flexible circuit members, suchas illustrated in FIGS. 10D-10I, in a back to back configuration.

[0060]FIG. 25 illustrates an alternate compliant interconnect assemblygenerally as illustrated in FIG. 21 with an additional circuitry planeis added to the structure.

[0061]FIG. 26 illustrates an alternate compliant interconnect assemblygenerally as illustrated in FIG. 24 with an additional circuitry planeis added to the structure.

[0062]FIG. 27 illustrates an alternate compliant interconnect assemblygenerally as illustrated in FIG. 21 with an additional circuitry planeis added to the structure.

[0063] FIGS. 28A-28D illustrate an alternate compliant interconnectassembly constructed with a plurality of discrete compliant members.

[0064]FIG. 29 illustrate a variation of the compliant interconnectassembly of FIG. 28A.

[0065]FIG. 30 is a top view of a compliant interconnect assemblygenerally as illustrated in FIGS. 21-29.

DETAILED DESCRIPTION OF THE INVENTION

[0066] FIGS. 1-4 illustrate a method of preparing a compliantinterconnect 22 in accordance with the present invention (see FIG. 5).The Figures disclosed herein may or may not be drawn to scale. Thesubstrate 20 is perforated to include one or more through holes 24. Theholes 24 can be formed by a variety of techniques, such as molding,stamping, laser drilling, or mechanical drilling. The holes 24 can bearranged in a variety of configurations, including one ortwo-dimensional arrays. As will be discussed below, some embodiments donot require the holes 24. The substrate 20 is typically constructed froma dielectric material, such as plastics, ceramic, or metal with anon-conductive coating. In some of the embodiments discussed below, anelectrically active circuit member (see FIG. 11) is substituted for theelectrically inactive substrate 20.

[0067] As illustrated in FIG. 2, the substrate 20 is then flooded withone or more masking materials 26, such as a solder mask or othermaterials. Through careful application and/or subsequent processing,such as planarization, the thickness of the masking material atlocations 28, 30 is closely controlled for reasons that will becomeclearer below. The additional holes 32 shown in FIG. 3 are then drilledor perforated in the substrate 20 and masking material 24 at apredetermined distance 36 from the existing through hole 24. While thereis typically a hole 32 adjacent each of the holes 24, there is notnecessarily a one-to-one correlation. The holes 32 can be arranged in avariety of configurations, which may or may not correlate to the one ortwo-dimensional array of holes 24.

[0068] The holes 32 are then filled with a compliant material 38, asshown in FIG. 4. The thickness of the compliant material 38 is typicallydetermined by the thickness of the masking material 26. Suitablecompliant materials include elastomeric materials such as Sylgard™available from Dow Corning Silicone of Midland, Mich. and MasterSyl'713, available from Master Bond Silicone of Hackensack, N.J.

[0069] The compliant interconnect 22 of FIGS. 2-4 can optionally besubjected to a precision grinding operation, which results in very flatsurfaces, typically within about 0.0005 inches. The grinding operationcan be performed on both sides at the same time using a lapping ordouble grinding process. In an alternate embodiment, only one surface ofthe compliant interconnect 22 is subject to the planarization operation.The present method permits the accurate manufacture of raised portions40 having virtually any height.

[0070] Once the compliant encapsulant 38 is cured, the masking material26 is removed to yield the compliant interconnect 22 illustrated in FIG.5. The compliant interconnect 22 illustrated in FIG. 5 includes thesubstrate 20, one or more compliant raised portions 40 of the compliantencapsulant 38 extending above the substrate 20, and the through holes24. The compliant raised portions can be, for example, thenon-conductive encapsulant 38 in FIG. 5 or the conductive member 171C ofFIG. 12C. The substrate can be a carrier or a circuit member, such as aprinted circuit board, a flexible circuit, a bare die device, anintegrated circuit device, organic or inorganic substrates, or a rigidcircuit. The through holes are optionally added for some applications.

[0071]FIG. 5 illustrates a compliant interconnect assembly 34 inaccordance with the present invention. The compliant interconnectassembly 34 includes the compliant interconnect 22 and one or moreflexible circuit members 50, 70. The first flexible circuit member 50 islocated along one surface of the compliant interconnect 22. The firstflexible circuit member 50 includes a polymeric sheet 52 and a series ofelectrical traces 54. In the embodiment illustrated in FIG. 5, thetraces 54 terminate at a contact pad 56. The electrical trace 54terminates in a solder ball 64. The contact pad 56 is positioned toengage with a contact pad 60 on a first circuit member 62. The solderball 64 is positioned adjacent to through hole 65. As used herein,“circuit member” refers to a printed circuit board, a flexible circuit,a packaged or unpackaged bare die silicon device, an integrated circuitdevice, organic or inorganic substrates, a rigid circuit, or a carrier(discussed below).

[0072] The region of the polymeric sheet 52 adjacent to the contact pad56 includes singulation 58. The singulation 58 is a complete or partialseparation of the terminal from the sheet 52 that does not disrupt theelectrical integrity of the conductive trace 54. In the illustratedembodiment, the singulation 58 is a slit surrounding a portion of thecontact pad 56. The slit may be located adjacent to the perimeter of thecontact pad 56 or offset therefrom. The singulated flexible circuitmembers 50, 70 control the amount of force, the range of motion, andassist with creating a more evenly distributed force vs. deflectionprofile across the array.

[0073] As used herein, a singulation can be a complete or partialseparation or a perforation in the polymeric sheet and/or the electricaltraces. Alternatively, singulation may include a thinning or location ofweakness of the polymeric sheet along the edge of, or directly behind,the contact pad. The singulation releases or separates the contact padfrom the polymeric sheet, while maintaining the interconnecting circuittraces.

[0074] The singulations can be formed at the time of manufacture of thepolymeric sheet or can be subsequently patterned by mechanical methodssuch as stamping or cutting, chemical methods such as photolithography,electrical methods such as excess current to break a connection, alaser, or a variety of other techniques. In one embodiment, a lasersystem, such as Excimer, CO₂, or YAG, creates the singulation. Thisstructure is advantageous in several ways, where the force of movementis greatly reduced since the flexible circuit member is no longer acontinuous membrane, but a series of flaps or bond sites with a livinghinge and bonded contact (see for example FIG. 10).

[0075] The second flexible circuit member 70 is likewise positioned onthe opposite side of the compliant interconnect 22. Electrical trace 72is electrically coupled to contact pad 74 positioned to engage with acontact pad 76 on a second circuit member 78. Solder ball 80 is locatedon the opposite end of the electrical trace 72. Polymeric sheet 82 ofthe second flexible circuit member 70 also includes a singulation 84adjacent to the contact pad 74.

[0076] The contact pads 56, 74 can be part of the base laminate of theflexible circuit members 50, 70, respectively. Alternatively, discretecontact pads 56, 74 can be formed separate from the flexible circuitmembers 50, 70 and subsequently laminated or bonded in place. Forexample, an array of contact pads 56, 74 can be formed on a separatesheet and laminated to the flexible circuit members 50, 70. Thelaminated contact pads 56, 74 can be subsequently processed to addstructures (see FIG. 20) and/or singulated.

[0077] The contact pads 60, 76 may be a variety of structures such as,for example, a ball grid array, a land grid array, a pin grid array,contact points on a bare die device, etc. The contact pads 60, 76 can beelectrically coupled with the compliant interconnect assembly 34 bycompressing the components 62, 78, 34 together (solderless), byreflowing solder or solder paste at the electrical interface, byconductive adhesive at the electrical interface, or a combinationthereof.

[0078] As illustrated in FIG. 6, the first and second flexible circuitmembers 50, 70 are compressed against the compliant interconnectassembly 34. The solder balls 64, 80 are reflown and create anelectrical connection between the first and second flexible circuitmembers 50, 70, generally within through hole 65. Adhesive 90 mayoptionally be used to retain the first and second flexible circuitmembers 50, 70 to the substrate 20. Contact pads 56, 74 are abuttedagainst raised portion 40 of the compliant material 38.

[0079] The singulations 58, 84 permit the raised portions 40 to push thecontact pads 56, 74 above the surface of the substrate 20, withoutdamaging the first and second flexible circuit members 50, 70,respectively. The raised portion 40 also deforms outward due to beingcompressed. The contact pads 56, 74 may optionally be bonded to theraised compliant material 40. The raised compliant material 40 supportsthe flexible circuit members 50, 70, and provides a contact force thatpresses the contact pads 56, 74 against the contact pads 60, 76 as thefirst and second circuit members 62, 78, respectively are compressedagainst the compliant interconnect assembly 34. The movement of thecontact pads 56, 74 is controlled by the raised portion 40 of thecompliant material 38 and the resiliency of the flexible circuit members50, 70. These components are engineered to provide a desired level ofcompliance. The raised portions 40 provide a relatively large range ofcompliance of the contact pads 56, 74. The nature of the flexiblecircuit members 50, 70 allow fine pitch interconnect and signal escaperouting, but also inherently provides a mechanism for compliance.

[0080] In the illustrated embodiment, the electric trace 54 extendsbetween solder ball 64 and contact pad 56. Similarly, the electric trace72 extends between the solder ball 80 and the contact pad 74.Consequently, the compliant interconnect assembly 34 operates as apass-through connector between the contact pad 60 on the first circuitmember 62 and the contact pad 76 on the second circuit member 78.

[0081]FIG. 7 illustrates an alternate substrate 100 with an array ofthrough holes 102. In the illustrated embodiment, masking material 104is applied to only one surface of the substrate 100 and the through hole102. Additional holes 106 are prepared in the masking material 104 andsubstrate 100 a fixed distance 108 from the hole 102, as illustrated inFIG. 8. The hole 106 is only drilled partially into the substrate 100. Acompliant material 110 is then deposited in the hole 106. After themasking material 104 is removed, the resulting compliant interconnect112 includes a raised compliant material only on one surface (seegenerally FIG. 11).

[0082]FIG. 10A is a perspective view of a flexible circuit member 120Asuitable for use in the present invention. The flexible circuit member120A includes a series of electrical traces 122A deposited on apolymeric sheet 124A and terminating at an array of contact pads orterminals 126A. As used herein “terminal” refers to an electricalcontact location or contact pad. In the illustrated embodiment, theterminals 126A include a singulation 128A. The degree of singulation128A can vary depending upon the application. For example, in someembodiments the flexible circuit member 120A stretches in order tocomply with the raised portions. In other embodiments a greater degreeof singulation minimizes or eliminates stretching of the flexiblecircuit member 120A due to engagement with the raised portions.

[0083] In some embodiments, the terminals 126A include one or morelocations of weakness 130A. As used herein, “locations of weakness”include cuts, slits, perforations or frangible portions, typicallyformed in the polymeric sheet 124A and/or a portion of the electricaltrace 122A forming the terminal 126A. The locations of weaknessfacilitate interengagement of an electrical contact, such as a ballcontact on a BGA device, with the terminal 126A (see FIG. 19). Theterminals 126A can optionally include an aperture 132A to furtherfacilitate engagement with an electrical contact. In another embodiment,a portion 134A of the trace 122A protrudes into the aperture 132A toenhance electrical engagement with the electrical contact.

[0084] In other embodiments, a compliant raise portion is attached tothe rear of the flexible circuit member 120A opposite the terminal 126A(see FIG. 11). When the flexible circuit member 120A is pressed againsta surface (such as a printed circuit board), the raised compliantmaterial lifts the singulated terminal 126A away from the surface.

[0085]FIG. 10B is a top plan view of an alternate flexible circuitmember 120B with an elongated singulation 128B. Contact pads 126B arelocated on the top of the polymeric sheeting 124B and the solder ballbonding sites 125B are located on the bottom. The contact pads 126B areoffset from the solder ball-bonding site 125B by the portion 127B of thepolymeric sheeting 124B. An electrical trace can optionally connect thecontact pads 125B with the contact pads 126B along the portion 127B. Theportion 127B permits the contact pads 126B to be raised up or deflectedfrom the flexible circuit member 120B in order to comply with the motionof the flexure (see for example FIGS. 11-15) with minimal or nodeformation or stretching of the surrounding polymeric sheeting 124B.The contact pads 126B can optionally include locations of weakness.

[0086]FIG. 10C is a top plan view of an alternate flexible circuitmember 120C with an irregularly shaped singulation 128C. Contact pads126C are located on the top of the polymeric sheeting 124C and thesolder ball bonding sites 125C are located on the bottom. The contactpads 126C are offset from the solder ball-bonding site 125C by theirregularly shaped portion 127C of the polymeric sheeting 124C. Theshape of the portion 127C determines the force required to raise up ordeflect the contact pads 126C from the flexible circuit member 120C inorder to comply with the motion of the flexure (see for example FIGS.11-15). Again, minimal or no deformation or stretching of thesurrounding polymeric sheeting 124C is experienced. An electrical trace121C can optionally connect some of the contact pads 125C with thecontact pads 126C along the portion 127C. Additionally, trace 129C canconnect two or more contact pads 125C, such as for a common groundplane.

[0087]FIG. 10D is a top plan view of a pattern of electrical traces 122Dof a flexible circuit member 120D prior to singulation. In theembodiment of FIG. 10D, the electrical traces 122D include tie bars 124Dinterconnecting a plurality of compliant members 126D. As will bediscussed below, distal ends 128D of the compliant members 126D can beeasily deformed out of the plane of the tie bars 124D to electricallycouple with other circuit members. For example, the distal ends 128D areconfigured to electrically couple with contact pads on an LGA device,while proximal ends 130D can electrically couple with a BGA device.Although the distal end 128D is generally linear, it can be configuredwith a variety of non-linear features, such as curvilinear or serpentineportions (see e.g., FIGS. 10F-10I). The electrical traces 122D arepreferably constructed from a copper alloy formed by chemical etching,laser ablation, mechanical stamping or a variety of other techniques.

[0088] The electrical traces 122D can optionally be attached to apolymeric sheet, such as illustrated in FIGS. 10A-10C. In anotherembodiment, the electrical traces 122D are attached to a carrier, suchas illustrated in FIG. 12C. The carrier can be rigid, semi-rigid, orflexible. The electrical traces 122D can be attached to a carrier usinga variety of techniques, such as lamination with or without adhesives,over molding, insert molding, and a variety of other techniques. In someembodiments, portions of the electrical traces 122D are sufficientlythick to operate as freestanding compliant members, such as illustratedin FIG. 12B.

[0089] In the preferred embodiment, the electrical traces 122D aresupported by a carrier that maintains the relative position of theindividual compliant members 126D after singulation. Singulation istypically accomplished by cutting or removing selected tie bars 124Dusing chemical etching, laser ablation or mechanical processes. Oneadvantage of the present embodiment is the ability to process an entirefield of compliant members 126D as a group. Many different geometries ofelectrical traces 122D are possible and are shaped based upon the typeof terminal to which it must connect.

[0090]FIG. 10E is a top plan view of a pattern of electrical traces 122Dof a flexible circuit member 120D of FIG. 10D after singulation. Theelectrical traces 122D are attached to a carrier (see e.g. FIG. 21) sothat the relative position of the compliant members 126D remainssubstantially unchanged even if all tie bars 124D are removed duringsingulation. In the embodiment illustrated in FIG. 10E, selected tiebars 124D are removed by chemical etching or laser ablation. Thecompliant members 132D connected by tie bars 124D form a ground plane orpower plane. The compliant members 134D that are disconnected from theelectrical traces 122D (i.e., discrete compliant members) typicallycarry electrical signals between the first and second circuit members(see FIG. 21).

[0091]FIG. 10F is a top plan view of a pattern of electrical traces 122Fof a flexible circuit member 120F prior to singulation. The electricaltraces 122F include tie bars 124F interconnecting a plurality ofcompliant members 126F. In the embodiment of FIG. 10F, each compliantmember 126F includes a pair of distal ends 128F, 130F. The distal ends128F, 130F of the compliant members 126F can be easily deformed out ofthe plane of the tie bars 124F to electrically couple with other circuitmembers. The distal ends 128F, 130F can be deformed in the same ordifferent directions, depending upon the application (see e.g., FIG.22). The curved portions 132F, 134F of the distal ends 128F, 130F areparticularly well suited to electrically couple with a BGA device. Thecurved portions 132F, 134F are adapted to create a snap-fit attachmentto a ball on BGA circuit member. Members 136F, 138F on the inside edgeof the curved portions 132F, 134F facilitate electrical coupling to aBGA device.

[0092]FIG. 10G is a top plan view of a pattern of electrical traces 122Gof a flexible circuit member 120G prior to singulation. Each compliantmember 126G includes a pair of distal ends 128G, 130G. The distal ends128G, 130G of the compliant members 126G can be easily deformed out ofthe plane of the tie bars 124G to electrically couple with other circuitmembers.

[0093]FIG. 10H similarly shows a top plan view of a pattern ofelectrical traces 122H of a flexible circuit member 120H prior tosingulation. Each compliant member 126H includes a pair of distal ends128H, 130H.

[0094]FIG. 10I is a top plan view of a pattern of electrical traces 122Iwhere each compliant member 126I includes a pair of curved distal ends128I, 130I. The curved portions 132I, 134I of the distal ends 128I, 130Iare particularly well suited to electrically couple with a BGA device.The curved portions 132I, 134I are adapted to create a snap-fitattachment to a ball on BGA circuit member.

[0095]FIG. 11 is a sectional view of an alternate compliant interconnectassembly 140 in accordance with the present invention. The raisedcompliant material 142 is formed directly on second circuit member 144,which in the embodiment of FIG. 11 is a printed circuit board. In analternate embodiment, the raised compliant material 142 are formedseparate from the second circuit member 144 and subsequently bondedthereto using a suitable adhesive or other bonding technique. In anotherembodiment, the raised portion 142 is formed on, or bonded to, the rearof flexible circuit member 146. In the illustrated embodiment, theprinted circuit board 144 serves the function of both the substrate 20and the second circuit member 78 illustrated in FIG. 5. The embodimentof FIG. 11 does not require through holes in the circuit member 144.

[0096] Flexible circuit member 146 includes a solder ball 148 that istypically reflown to electrically couple bonding pad 150 to the contactpad 152 on the circuit board 144. Alternatively, solder paste can beapplied to both the bonding pad 150 and the contact pad 152. Electricaltrace 154 electrically couples the solder bonding pad 150 to contact pad156. Contact pad 156 may optionally include a rough surface to enhancethe electrical coupling with the contact pad 160 on the first circuitmember 162. The flexible circuit member 146 is singulated so that theraised compliant material 142 lifts the contact pad 156 away from thecircuit member 144. When the circuit member 162 is compressed againstthe compliant interconnect assembly 140, the raised compliant material142 biases the contact pad 156 against the first circuit member 162. Inthe compressed state, the compliant interconnect assembly 140 can have aheight of about 0.3 millimeters or less. Alternatively, the contact pad160 can be electrically coupled with the contact pad 156 by reflowingsolder or solder paste at the electrical interface, by conductiveadhesive at the electrical interface, or either of the above incombination with compression.

[0097] The raised compliant material 142 can optionally be doped orfilled with rigid or semi-rigid materials to enhance the integrity ofthe electrical contact created with the contact pad 160 on the firstcircuit member 162. Bonding layer 164 is optionally provided to retainthe contact pad 156 to the raised compliant material 142.

[0098]FIG. 12A illustrates an alternate compliant interconnect assembly170 using a compliant interconnect generally as illustrated in FIGS.7-9. Raised compliant material 172 is attached to a carrier 174 that isinterposed between first and second circuit members 176, 178. Thecarrier 174 can be rigid or flexible. An additional support layer 182can optionally be added to the carrier 174 to increase rigidity and/orcompliance. In one embodiment, the raised compliant material 172 has afirst modulus of elasticity and the additional support layer 182 has asecond modulus of elasticity different from the first modulus ofelasticity. In another embodiment, the raised compliant material 172 isattached to the rear surface of flexible circuit member 184.

[0099] Flexible circuit member 184 is electrically coupled to thecontact pad 186 on second circuit member 178 by solder ball or solderpaste 188. When the first circuit member 176 is compressively engagedwith the compliant interconnect assembly 170, raised compliant material172 biases contact pad 190 on the flexible circuit member 184 againstcontact pad 192 on the first circuit member 176. In an embodiment wherethe carrier 174 has compliant properties, the combined compliantproperties of the carrier 174 and raised compliant material 172 providesthe bias force.

[0100] In another embodiment, the flexible circuit member 184 extends toa second interconnect assembly 170A. Any of the interconnect assembliesdisclosed herein can be used as the interconnect assembly 170A. In theillustrated embodiment, raised compliant material 172A is attached to acarrier 174A that is interposed between first circuit members 176 and athird circuit member 194. The carrier 174A can be rigid or flexible. Anadditional support layer 182A can optionally be added to the carrier174A to increase rigidity and/or compliance. The third circuit member194 can be an integrated circuit device, such as the LGA deviceillustrated in FIG. 12A, a PCB or a variety of other devices. The entireassembly of circuit members 176, 178, 194 can be stacked together andthe solder then mass reflowed during final assembly.

[0101]FIG. 12B illustrates an alternate compliant interconnect assembly170B generally as illustrated in FIG. 12A, except that the raisedcompliant material 172B attached to a carrier 174B is an elongatedcompliant member 171B. The compliant member 171B can be spring member ora rigid member attached to a compliant carrier 174B, such as a berylliumcopper spring. An additional support layer 182B can optionally be addedto the carrier 174B to increase rigidity and/or compliance. Thecompliant members 171B provide reactive support to urge the contact pad190B on the flexible circuit member 184B against the contact pad 192B onthe first circuit member 176B. The compliant member 171B can be formedin the carrier 174B or formed separately and attached thereto. Thecompliant member 171B can alternatively be a coil spring or a variety ofother structures.

[0102]FIG. 12C illustrates another alternate compliant interconnectassembly 170C generally as illustrated in FIG. 12B, except that theraised compliant material 172C is an elongated compliant member 171Csupporting the flexible circuit member 184C. Substrate 174C includes aseries of compliant spring members 171C positioned under the flexiblecircuit member 184C. The upper surface of the flexible circuit member184C is patterned with a series of rough contact pads 190C. The lowersurface of the flexible circuit member 184C is prepared to receivesolder paste or solder ball 194C. The rigid substrate 174C also includesa series of solder deposit alignment openings 175C through which solderball 194C can couple the lower surface of the flexible circuit member184C with second circuit member 198C. The compliant members 171C providereactive support to bias the flexible circuit member 184C againstcontact pad 192C on first circuit member 176C.

[0103]FIG. 12D illustrates another alternate compliant interconnectassembly 170D generally as illustrated in FIG. 12C, except that theraised compliant material 172D operates without the polymeric sheetingof a flexible circuit member. The thickness of the compliant member 172Dcan be engineered to provide the desired amount of resiliency. Substrate174D includes a series of conductive compliant members 171D positionedto engage with the contact pad 192D on the first circuit member 176D.The lower surface of the conductive compliant member 171D is prepared toreceive solder paste or solder ball 194D. The substrate 174D alsoincludes a series of solder deposit alignment openings 175D throughwhich solder ball 194D can couple the lower surface of the conductivecompliant members 171D with second circuit member 198D.

[0104]FIG. 13 illustrates an alternate compliant interconnect assembly200 in accordance with the present invention. A pair of discretecompliant raised portions 202, 204 are attached to a carrier 206. In theillustrated embodiment, the carrier 206 is a multi-layered structure.First and second flexible circuit members 210, 212 are positioned onopposite sides of the compliant interconnect assembly 200, generally asillustrated in FIG. 6. Solder ball 214 connects solder ball pads 216,218 on the respective flexible circuit members 210, 212. The solder ball214 can be replaced by a variety of connection methods such as wedgebonding, ultrasonic bonding, resistance bonding, wire bonding, oriso-tropic/anisotropic conductive adhesives.

[0105] Contact pads 220, 222 on the respective flexible circuit members210, 212 are singulated. Adhesive 221 can optionally be used to bondcontact pads 220, 222 to the raised compliant material 202, 204. Theflexible circuit members 210, 212 can optionally be bonded to thecarrier 206. The resulting compliant interconnect assembly 200 isinterposed between first and second circuit members 226, 228 in acompressive relationship so that contact pads 220, 222 are compressivelyengaged with respective contact pads 230, 232.

[0106]FIG. 14A illustrates an alternate compliant interconnect assembly300 in accordance with the present invention. The raised compliantmaterial 302 is located on the first circuit member 304. The raisedcompliant material 302 can be bonded to both the first circuit member304 and the rear of contact pad 314. In the illustrated embodiment, thefirst circuit member 304 is a packaged integrated circuit device. Thefirst circuit member 304 can alternately be a printed circuit board,another flexible circuit, a bare-die device, an integrated circuitdevice, an organic or inorganic substrate, a rigid circuit and virtuallyany other type of electrical component. Solder ball pad 306 on theflexible circuit member 308 is electrically coupled to contact pad 310on the first circuit device 304 by solder ball 312. Contact pad 314 onthe flexible circuit member 308 is supported by raised compliantmaterial 302. The contact pad 314 can be compressively engaged with pad316 on the second circuit member 318.

[0107] In an alternate embodiment, FIG. 14A illustrates aconnector-on-package 320 in accordance with the present invention. Thefirst circuit device 304 forms a substrate for package 322 containingbare die device 324. In the illustrated embodiment, the bare die device324 is a flip chip and/or wire bond integrated circuit structure,although any packaged integrated circuit device can be used in thepresent connector on package 320 embodiment. The compliant interconnectassembly 300 is formed on the substrate 304 as discussed above, yieldinga packaged integrated circuit 324 with an integral connector 300.

[0108]FIG. 14B illustrates an alternate compliant interconnect assembly300B generally as shown in FIG. 14A. Contact pad 305B on the flexiblecircuit member 308B is electrically coupled directly to the contact pad310B on the first circuit member 304B. The raised compliant material302B is attached to the circuit member 304B and is reduced in height tocompensate for the height loss due to removal of the solder ball. Thefirst circuit member 304B can be a printed circuit board, anotherflexible circuit, a bare-die device, an integrated circuit device, anorganic or inorganic substrate, a rigid circuit and virtually any othertype of electrical component.

[0109]FIG. 15A illustrates an alternate compliant interconnect assembly400 in accordance with the present invention. Raised compliant material402 is mounted on a carrier 404 that is positioned adjacent to the firstcircuit member 406. In the illustrated embodiment, the first circuitmember 406 is a packaged integrated circuit device. The carrier 404 canbe optionally bonded to the first circuit member 406. Ball grid array(BGA) solder ball 408 (or solder paste) is used to electrically couplecontact pad 410 on the first circuit member 406 with the solder ball pad412 on the flexible circuit member 414. The singulated contact pad 416on the flexible circuit member 414 is supported by the raised compliantmaterial 402 for compressive engagement with contact pad 418 on thesecond circuit member 420.

[0110] In one application, the embodiment of FIG. 15A can be used to“connectorize” a conventional BGA device 422 by adding the compliantinterconnect assembly 400. In essence, the compliant interconnectassembly 400 can be merged into an existing BGA device 422 to form anassembly 401 comprising the packaged integrated circuit 406 and thecompliant interconnect assembly 400. The contact pads 416 can simply bepushed against the PCB 420 to create a solderless connection withoutactually mounting a connector on the PCB 420. Alternately, solder at theinterface of the contact pads 416, 418 can be reflowed. The assembly 401can be provided as a conversion kit for integrated circuit devices,thereby eliminating the need for a connector on the printed circuitboard 420. The connectorized embodiment of FIG. 15A can be used with anytype of packaged integrated circuit, such as an LGA, PLCC, PGA, SOIC,DIP, QFP, LCC, CSP, or other packaged or unpackaged integrated circuits.

[0111]FIG. 15B illustrates an alternate connectorized integrated circuitdevice 424 in accordance with the present invention. The compliantinterconnect 434 includes raised compliant material 425 mounted on acarrier 426. Singulated contact pad 427 on flexible circuit member 428is supported by the raised compliant material 426 for compressiveengagement with contact pad 429 on the first circuit member 430. Theconnection between the contact pads 427, 429 can be created bycompression or the reflow of solder. Integrated circuit device 431 isdirect connected to the flexible circuit member 428. The integratedcircuit device 431 can be electrically coupled to the flexible circuitmember 428 by flip chip bumps 432 and/or wire bonds 433. Alternatively,terminals 436 on the integrated circuit device 431 can include locationsof weakness (see FIG. 10A) that permit the bumps 432 to be snap-fit withthe flexible circuit member 428 (see FIG. 19). The integrated circuitdevice can be an unpackaged bare die device. In one embodiment, theintegrated circuit device 431, the compliant interconnect 434 and aportion of the flexible circuit member 428 can be retained in package435.

[0112]FIG. 16 is a perspective view of a replaceable chip module 440coupled to a flexible circuit member 454 using a compliant interconnectassembly in accordance with the present invention. The housing 442includes a plurality of device sites 444, 446, 448, 450 configured toreceive various first circuit members. The housing 442 can be aninsulator housing or an alignment frame, typically constructed fromplastic or shielded metal.

[0113] In one embodiment, the replaceable chip module 440 illustrated inFIG. 16 includes a second circuit member 451, such as a PCB, having a168 DIMM edge card connector 452 along one edge. Flex circuit member 454is interposed between the second circuit member 451 and the housing 442to form compliant interconnect assemblies 458 at one or more of thedevice sites 444, 446, 448, 450. Various integrated circuit devices canbe located at the device sites 444, 446, 448, 450. The flexible circuitmember 454 may extend across the entire second circuit member 451, orjust a portion thereof. Any of the compliant interconnect assembliesdisclosed herein can be used for this purpose. The raised compliantmaterial can correspondingly be formed on the first or second circuitmembers, or the substrate (see for example FIG. 5).

[0114] In another embodiment, the second circuit member 451 is anextension of the flexible circuit member 454. Stiffener 443 isoptionally provided behind the flexible circuit member 451.

[0115] The housing 442 includes a device site 444 for receiving amicroprocessor device. Along one edge of the housing 442 are a series ofdevice sites 446 configured to receive flash memory integrated circuitdevices. Device sites 448, 450 are provided along the other edges of thehousing 442 for receiving other circuit members supportive of themicroprocessor. Each of the device sites 444, 446, 448, 450 optionallyinclude appropriate covers 456 a-456 c. The covers 456 a-456 c havebeveled edges 449 for sliding engagement with a corresponding lips 453on the housing 442.

[0116] The flexible circuit member 454 extends beyond the housing 442,permitting it to perform more functions than simple providing aninterconnect between the first and second circuit members. For example,the flexible circuit member 454 can include integrated ground planes;buried passive functions such as capacitance; redistribution of terminalrouting or pitch; and/or leads to bring in other signals or power fromexternal sources to the device being connected without having to come inthrough the PCB 451. Using the flexible circuit member to perform otherfunctions reduces the number of terminals need to be connected to themain PCB 451 since all of the ground pins from the first circuit memberscan be coupled to the flex circuit and/or the substrate. Anotheradvantage of this embodiment is that it is possible to alter the signalsor power coming in through the flexible circuit member 454, such asfiltering, amplifying, decoupling etc.

[0117]FIG. 17 is a side sectional view of an assembly 468 comprisingmultiple compliant interconnect assemblies 470, 472 arranged in astacked configuration with multiple circuit members 474, 476, 478 inaccordance with the present invention. The interconnect assemblies 470,472 correspond generally with those illustrated in FIG. 6, although anyof the interconnect assemblies disclosed herein can be arranged in astacked configuration. The circuit members 474, 476, 478 can be printedcircuit boards, flexible circuits, bare-die devices, integrated circuitdevices, organic or inorganic substrates, rigid circuits or combinationsthereof. The assembly 468 is typically located in a housing (see FIG.16) to maintain alignment and a compressive relationship with thevarious components. The four flexible circuit members 480, 482, 484, 486can be arrange parallel to each other or at various angles.Additionally, the flexible circuit members 480, 482, 484, 486 can beconnected to each other, such as the connection 498 connecting flexiblecircuit member 482 to flexible circuit member 484. FIG. 18 illustratesone possible arrangement of the flexible circuit members 480, 482, 484,486 layered together with the circuit member 474 on top of the assembly468. Distal ends 490, 492, 494, 496 of the various flexible circuitmembers 480, 482, 484, 486 are free to connect to other circuits.

[0118]FIG. 19 illustrates an alternate compliant interconnect assembly500 using a compliant interconnect generally as illustrated in FIG. 12A.Raised compliant material 502 is attached to a carrier 504 that isinterposed between first and second circuit members 506, 508. Thecarrier 504 can be rigid or flexible. An additional support layer 510can optionally be added to the carrier 504 to increase rigidity and/orcompliance. Flexible circuit member 512 is electrically coupled to thecontact pad 514 on second circuit member 508 by solder ball or solderpaste 516. When the first circuit member 506 is compressively engagedwith the compliant interconnect assembly 500, raised compliant material502 biases contact pad 518 on the flexible circuit member 512 againstcontact pad 520 on the first circuit member 506.

[0119] In one embodiment, the flexible circuit member 512 extends to athird circuit member 522. The third circuit member 522 can beelectrically coupled using any of the techniques disclosed herein,including the connectorized approach illustrated in FIG. 15B. In theillustrated embodiment, terminals 524 on the flexible circuit 512include an aperture 526 and a plurality of locations of weakness 528(see FIG. 10A). The locations of weakness 528 permit solder ball 530 tosnap-fit into aperture 526 to form a strong mechanical interconnect. Thesolder ball 530 can optionally be reflowed to further bind with theterminal 524. If the solder ball 530 is reflowed, the segmented portionsof the terminal 524 will flex into the molten solder. When the soldersolidifies, the terminal 524 will be at least partially embedded in thesolder ball 530. The third circuit member 522 can be an integratedcircuit device, such as an LGA device, BGA device, CSP device, flipchip, a PCB or a variety of other devices.

[0120]FIG. 20 is a schematic illustration of various conductivestructures 556 formed on the contact pads 554 of flexible circuit member550. The conductive structures 556 facilitate electrical coupling withvarious types of contact pads on a circuit member. The structures 556can be metal pieces soldered to the contact pads 554, a build-up ofsolder or conductive adhesive or other conductive members bonded to thecontact pads 554. Structures 560 and 562 include generally flat uppersurfaces 564 suitable to engage with an LGA device. Structure 566includes a recess 568 generally complementary to the contact pads on aBGA device. Structure 570 includes a series of small protrusions 572designed to frictionally engage with various contact pads. Structure 558is a solder bump, such as may be found on a BGA device. The conductivestructures 556 can be coupled with a circuit member using compressionand/or reflowing the solder.

[0121]FIG. 21 illustrates an alternate compliant interconnect assembly600 using an electrical trace 602 generally as illustrated in FIGS.10D-10I. The electrical trace 602 is attached to carrier 604. Thecarrier 604 can be a rigid or a flexible dielectric material. After theelectrical trace 602 is singulated, a second dielectric carrier 606 canoptionally be located on the opposite surface. Distal ends 608 of thecompliant members 610 are deformed to extend through openings 612 in thecarrier 604.

[0122] In the illustrated embodiment, the distal end 608 is deformed ina first direction and a solder ball 614 is electrically coupled to theproximal end of the compliant member 610. When a first circuit member616 is compressively engaged with the compliant interconnect assembly600, distal end 608 of the compliant member 610 electrically coupleswith contact pad 618 on the first circuit member 616. Solder ball 614 ispreferably melted to electrically couple with contact pad 620 on secondcircuit member 622. The embodiment of FIG. 21 is particularly suited toreleasably attaching a bare die device 616 to a printed circuit board622.

[0123] The compliant interconnect assembly 600 is typically constructedby etching electrical trace 602. A photoresist is printed onto tie barsthat are to be removed. The distal ends 608 are then deformed and theelectrical trace 602 is plated. The photoresist is then removed and theelectrical trace 602 is laminated to the carrier 604. An acid bath isused to etch away the tie bars that were previously covered with thephotoresist. The carrier 604 holds the compliant members 610 inposition. The second dielectric carrier 606 is then optionally laminatedto the opposite side of the electrical trace 602.

[0124]FIG. 22 illustrates an alternate compliant interconnect assembly630 using an electrical trace 632 generally as illustrated in FIGS.10F-10I. The electrical trace 632 is attached to carrier 634. After theelectrical trace 632 is singulated, a second dielectric carrier 636 canoptionally be located on the opposite surface. In the embodiment of FIG.22, each compliant member 638 includes at least two distal ends 640,642. The distal end 640 is deformed to extend through openings 644 inthe carrier 634 and the distal end 642 is deformed to extend through theopening 646 in the carrier 636.

[0125] When a first circuit member 648 is compressively engaged with thecompliant interconnect assembly 630, distal end 640 electrically coupleswith contact pad 650 on the first circuit member 648. Similarly, asecond circuit member 652 can be compressively engaged with the distalend 642 to electrically couples with contact pad 654 on the secondcircuit member 652.

[0126]FIGS. 23 and 24 illustrate a compliant interconnect assembly 660with a first electrical trace 662 attached to carrier 664. The firstelectrical trace 662 is singulated and the distal ends 666 of thecompliant members 668 are deformed. Similarly, a second electrical trace670 is attached to a carrier 672, singulated and the distal ends 674 ofthe compliant members 676 deformed. The electrical traces 662, 670 areplaced in a back to back configuration so that the respective compliantmembers 668, 676 are electrically coupled.

[0127] In the embodiment of FIG. 23, the compliant members 668, 674include holes 686, 688 that can be electrically coupled using amechanical connection such as a conductive plug or rivet, a heat stake,spot or ultrasonic welding, solder, compression, a coined feature thatflattens against the opposing compliant member, electrical plating, or avariety of other methods.

[0128] In the embodiment of FIG. 24, the compliant members 668, 676 areelectrically coupled by melting solder 690 between the joint, using thecarriers 664, 672 as a solder mask to prevent solder from wicking up thedistal ends 666, 674. Alternatively, the compliant members 668, 676 canbe electrically coupled using compression, solder paste, conductiveadhesive, spot or ultrasonic welding, a coined feature that flattensagainst the opposing compliant member, or a variety of other techniques.In one embodiment, The distal ends 666, 674 are electrically coupledwith contact pads 678, 680 on respective first and second circuitmembers 682, 684, as discussed in connection with FIGS. 21 and 22.

[0129]FIG. 25 illustrates an alternate compliant interconnect assembly700 generally as illustrated in FIG. 21, except that an additionalcircuitry plane 702 is added to the structure. For example, thecircuitry plane 702 can be a power plane, a ground plane, or aconnection to an external integrated circuit device 704. The circuitryplane 702 is preferably electrically isolated between carriers 708, 710,although some of the compliant members 713 can be electrically coupledto the circuitry plane 702. Optional carrier 706 can be provided. In theillustrated embodiment, the circuitry plane 702 extends beyond theboundaries of the compliant interconnect assembly 700 to facilitateconnection to a power source, a ground plane, or an external devices704. For example, the compliant interconnect assembly 700 can beinserted into the replaceable chip module 400 of FIG. 16, electricallycoupling the circuitry plane 702 to the flexible circuit member 454 orthe edge card connector 452.

[0130] As discussed in connection with FIG. 10E, a portion of theelectrical trace 712 can serve as a ground plane or power plane in someembodiments. The present compliant interconnect assembly 700 providesfor internal or embedded passive features such as decoupling capacitanceas a result of the layered power plane 702 and the ground plane providedby a portion of the electrical trace 712. In yet another embodiment,discrete electrical components 714, such as capacitors, can be added tothe present compliant interconnect assembly 700. The circuitry plane 702of the present embodiment improves the operating performance of thefirst and second circuit members 716, 718.

[0131]FIG. 26 illustrates an alternate compliant interconnect assembly750 generally as illustrated in FIGS. 23 and 24, except that anadditional circuitry plane 752 is added to the structure. Again, thecircuitry plane 752 can be a power plane, a ground plane, or aconnection to an external integrated circuit device 754. The circuitryplane 752 preferably extends beyond the boundaries of the compliantinterconnect assembly 750 to facilitate connection to a power source orexternal devices 754. The circuitry plane 752 is preferably electricallyisolated between dielectric layers 762, 764. The present compliantinterconnect assembly 750 provides for internal or embedded passivefeatures such as decoupling capacitance as a result of the layered powerplane 752 and the ground plane provided by a portion of the electricaltraces 756, 758. Discrete electrical components 760, such as capacitors,can optionally be added to the present compliant interconnect assembly750.

[0132]FIG. 27 illustrates an alternate compliant interconnect assembly770 generally as illustrated in FIG. 22, except that an additionalcircuitry plane 772 is added to the structure. Again, the circuitryplane 772 can be a power plane or a connection to an external integratedcircuit device 774. The circuitry plane 772 preferably extends beyondthe boundaries of the compliant interconnect assembly 770 to facilitateconnection to a power source or external devices 774. The presentcompliant interconnect assembly 770 provides for internal or embeddedpassive features such as decoupling capacitance as a result of thelayered power plane 772 and the ground plane provided by a portion ofthe electrical traces 776 attached to carrier 782. The circuitry plane772 is preferably sandwiched between layers of dielectric material 778,780. Discrete electrical components 784, such as capacitors, canoptionally be added to the present compliant interconnect assembly 770.

[0133] FIGS. 28A-28D illustrate various aspects of an alternatecompliant interconnect assembly 800 in accordance with the presentinvention. As discussed in connection with FIGS. 21-27, the flexiblecircuit member is preferably attached to a carrier before singulation soto retain the spatial relationship of the compliant members (see FIGS.10D-10I). In the embodiment of FIGS. 28A-28D, the flexible circuitmember, which is typically a sheet of conductive material, is singulatedprior to attachment to carrier 806 to form a plurality of discretecompliant members 804. The discrete compliant members 804 are attachedto a carrier 806 using a variety of techniques, such as thermal orultrasonic bonding, adhesives, mechanical attachment, and the like.

[0134] In the illustrated embodiment, the carrier 806 includes pairs ofadjacent slots 808, 810. Center portion 812 of the carrier 806 betweenthe slots 808, 810 acts as a torsion bar. A discrete compliant member804 is inserted though the slot 808 and attached to the center portion812, preferably by crimping. Alternatively, the compliant members 804can be attached to the carrier 806 through single slot 814. Upper andlower dielectric layers 816, 818 are preferably added to the top andbottom of the compliant interconnect assembly to prevent shorting orcontact rollover during compression. An additional circuitry plane 820and dielectric covering layer 822, as discussed above, can also be addedto the present compliant interconnect assembly 800.

[0135] As best illustrated in FIGS. 28C and 28D, the center portion 812twists and/or deforms to permit the compliant members 804 to compensatefor non-planarity in the first and second circuit members 824, 826 (seeFIG. 28a). Distal ends 828, 830 of the compliant members 804 also flexwhen compressed by the first and second circuit members 824, 826. Theamount of displacement and the resistance to displacement can beadjusted by changing the size and shape of the center portion 812 on thecarrier 806, and/or by constructing the carrier 806 from a more rigid orless rigid material that resists displacement of the compliant members804. In one embodiment, a flexible circuit member, such as shown inFIGS. 10D-10I is attached to the carrier 806. The combination of theflexible circuit member and the discrete compliant members providesmaximum flexibility in constructing the present compliant interconnectassembly 800.

[0136]FIG. 29 illustrates a variation of the compliant interconnectassembly 800 of FIGS. 28A-28D. The compliant interconnect assembly 840includes a plurality of discrete compliant members 842 attached to acarrier 844 as discussed above. Distal end 846 is positioned toelectrically couple with contact pad 848 on first circuit member 850.Solder ball 852 replaces the distal end 830 in FIG. 28A. The solder ball852 is positioned to electrically couple with contact pad 854 on secondcircuit member 856.

[0137]FIG. 30 is a top view of a compliant interconnect assembly 900 asshown in FIGS. 21-29. Carrier 902 includes an array of holes 904 throughwhich distal ends of the compliant members extend to engage with circuitmembers (see FIGS. 21-29). Any additional circuit planes (see FIGS.25-26) are preferably ported from the side of the compliant interconnectassembly 900, preferably by flexible circuit members 906, 908.

[0138] The embodiments disclosed herein are basic guidelines, and arenot to be considered exhaustive or indicative of the only methods ofpracticing the present invention. There are many styles and combinationsof properties possible, with only a few illustrated. Each connectorapplication must be defined with respect to deflection, use, cost,force, assembly, & tooling considered.

[0139] Patents and patent applications disclosed herein, including thosecited in the background of the invention, are hereby incorporated byreference. Other embodiments of the invention are possible. It is to beunderstood that the above description is intended to be illustrative,and not restrictive. Many other embodiments will be apparent to those ofskill in the art upon reviewing the above description. The scope of theinvention should, therefore, be determined with reference to theappended claims, along with the full scope of equivalents to which suchclaims are entitled.

What is claimed is:
 1. A compliant interconnect assembly comprising: afirst carrier having a first major surface and a plurality of throughopenings; a first flexible circuit member comprising a plurality ofelectrical traces having a first major surface attached to the firstmajor surface of the first carrier, the electrical trace comprising aplurality of compliant members having at least one distal end projectingin one of the openings of the first carrier; and a second carrier havinga first major surface positioned opposite a second major surface of thefirst flexible circuit member, the second carrier having a plurality ofthrough openings aligned with the plurality of the compliant members. 2.The compliant interconnect assembly of claim 1 wherein the distal end isdeformed to project through an opening in the first carrier.
 3. Thecompliant interconnect assembly of claim 1 wherein the distal end isdeformed to extend through an opening in the first carrier and to extendabove a second major surface of the first carrier.
 4. The compliantinterconnect assembly of claim 1 wherein the distal end comprises twodistal ends.
 5. The compliant interconnect assembly of claim 1 whereinthe distal end comprises a curvilinear shape.
 6. The compliantinterconnect assembly of claim 1 wherein the distal end comprises afirst distal end deformed to project in an opening in the first carrierand a second distal end deformed to project in an opening in the secondcarrier.
 7. The compliant interconnect assembly of claim 1 comprisingsolder balls located in the openings in the second carrier andelectrically coupled with the compliant members.
 8. The compliantinterconnect assembly of claim 1 comprising a first circuit memberhaving contact pads aligned with, and electrically coupled to, thedistal ends of the compliant members.
 9. The compliant interconnectassembly of claim 1 wherein the first circuit member comprises one of aprinted circuit board, a flexible circuit, a bare die device, anintegrated circuit device, organic or inorganic substrates, or a rigidcircuit.
 10. The compliant interconnect assembly of claim 1 comprising asecond circuit member having contact pads aligned with the holes in thesecond carrier, the second circuit member being electrically coupled tothe compliant members through the holes in the second carrier.
 11. Thecompliant interconnect assembly of claim 10 wherein the second circuitmember is electrically coupled to the compliant members by solder. 12.The compliant interconnect assembly of claim 10 wherein a distal end ofa compliant member extends through the holes in the second carrier toelectrically couple with the second circuit member.
 13. The compliantinterconnect assembly of claim 1 comprising an additional circuitryplane attached to a second major surface of the second carrier, theadditional circuitry plane comprising a plurality of through openingsaligned with a plurality through openings in the second carrier.
 14. Thecompliant interconnect assembly of claim 13 wherein the additionalcircuitry plane comprises one of a ground plane, a power plane, or anelectrical connection to other circuit members.
 15. The compliantinterconnect assembly of claim 1 comprising one or more discreteelectrical components electrically coupled to the first flexible circuitmember.
 16. The compliant interconnect assembly of claim 15 wherein theone or more discrete electrical components comprise capacitors.
 17. Thecompliant interconnect assembly of claim 1 comprising: a second flexiblecircuit member comprising a plurality of electrical traces having afirst major surface attached to the first major surface of the secondcarrier, the electrical trace comprising a plurality of compliantmembers having at least one distal end projecting in one of the openingsof the second carrier; and an electrical connection between thecompliant members on the first flexible circuit member and the compliantmembers on the second flexible circuit member.
 18. The compliantinterconnect assembly of claim 17 comprising a dielectric layer locatedbetween the first and second flexible circuit members.
 19. The compliantinterconnect assembly of claim 17 wherein the electrical connectioncomprises solder.
 20. The compliant interconnect assembly of claim 17wherein the electrical connection comprises a conductive plug.
 21. Thecompliant interconnect assembly of claim 17 wherein the electricalconnection comprises a compressive relationship between the compliantmembers on the first and second flexible circuit members.
 22. Thecompliant interconnect assembly of claim 17 wherein the electricalconnection comprises a conductive adhesive.
 23. The compliantinterconnect assembly of claim 17 comprising an additional circuitryplane interposed between the first and second flexible circuit members.24. The compliant interconnect assembly of claim 23 wherein at least onemajor surface of the additional circuitry plane comprises a dielectriclayer.
 25. The compliant interconnect assembly of claim 17 comprising asecond circuit member having contact pads aligned with, and electricallycoupled to, the distal ends of the compliant members on the secondflexible circuit member.
 26. The compliant interconnect assembly ofclaim 25 wherein the second circuit member comprises a bare die device.27. The compliant interconnect assembly of claim 1 wherein a portion ofthe first flexible circuit member extends beyond the compliantinterconnect assembly to permit electrical coupling with another circuitmember.
 28. The compliant interconnect assembly of claim 1 wherein theelectrical traces are singulated so that a portion of the compliantmembers are electrically isolated from the electrical traces.
 29. Thecompliant interconnect assembly of claim 1 wherein a portion of thecompliant members are electrically coupled to form a ground plane or apower plane.
 30. The compliant interconnect assembly of claim 1 whereinthe distal ends of the first flexible circuit member are adapted toengage with a connector member selected from the group consisting of aflexible circuit, a ribbon connector, a cable, a printed circuit board,a ball grid array (BGA), a land grid array (LGA), a plastic leaded chipcarrier (PLCC), a pin grid array (PGA), a small outline integratedcircuit (SOIC), a dual in-line package (DIP), a quad flat package (QFP),a leadless chip carrier (LCC), a chip scale package (CSP), or packagedor unpackaged integrated circuits.
 31. The compliant interconnectassembly of claim 1 wherein the second carrier is attached to a printedcircuit board and the compliant members are electrically coupled tocontact pads on the printed circuit board through the openings in thesecond carrier.
 32. The compliant interconnect assembly of claim 1wherein the distal ends of the compliant member are adapted to receive asolder ball on a circuit member in a snap-fit configuration.
 33. Thecompliant interconnect assembly of claim 1 wherein a portion of thefirst flexible circuit member extends beyond the compliant interconnectassembly to form a stacked configuration other compliant interconnectassemblies.
 34. The compliant interconnect assembly of claim 1 whereinthe carrier comprises a rigid material.
 35. The compliant interconnectassembly of claim 1 wherein the carrier comprises a flexible material.36. A compliant interconnect assembly comprising: a first carrier havinga first major surface and a plurality of through openings; at least onediscrete compliant member extending through one of the openings in thefirst carrier and attached to the first carrier adjacent to the opening,the compliant member having at least one distal end projecting away fromthe first carrier; a second carrier having a first major surfacepositioned opposite the first major surface of the first carrier, thesecond carrier having a plurality of openings through which the distalends of the compliant members extend.
 37. The compliant interconnectassembly of claim 36 comprising plurality of electrical traces attachedto the first major surface of the first carrier, the electrical tracecomprising a plurality of compliant members having at least one distalend projecting in one of the openings of the first carrier.
 38. Thecompliant interconnect assembly of claim 36 wherein the compliantmembers comprise two distal ends projecting away from opposite sides ofthe first carrier.
 39. The compliant interconnect assembly of claim 36comprising solder balls electrically coupled to the compliant membersand projecting away from a second major surface of the first carrier.40. The compliant interconnect assembly of claim 36 comprising a thirdcarrier having a first major surface positioned opposite a second majorsurface of the first carrier, the third carrier having a plurality ofopenings aligned with the compliant members.
 41. A method of making acompliant interconnect assembly, the method comprising the steps of:preparing a first carrier with a first major surface and a plurality ofthrough openings; preparing a first flexible circuit member having aplurality of electrical traces comprising a plurality of compliantmembers; attaching a first major surface of the first flexible circuitmember to the first major surface of a first carrier so that distal endsof the compliant members project in one of the openings in the firstcarrier; singulating the first flexible circuit member so that a portionof the compliant members are electrically isolated from the electricaltraces; preparing a second carrier with a first major surface and aplurality of through openings; positioning the second carrier opposite asecond major surface of the first flexible circuit member so that thethrough openings in the second carrier are aligned with compliantmembers.
 42. The method of claim 41 comprising deforming the distal endof the compliant members to project through an opening in the firstcarrier.
 43. The method of claim 41 comprising deforming the distal endof compliant members to extend through an opening in the first carrierand to extend above a second major surface of the first carrier.
 44. Themethod of claim 41 wherein the distal end comprises first and seconddistal ends, the method comprising deforming the first distal end toproject in an opening in the first carrier and deforming the seconddistal end to project in an opening in the second carrier.
 45. Themethod of claim 41 comprising locating solder balls in the openings inthe second carrier and electrically coupling the solder balls with thecompliant members.
 46. The method of claim 41 comprising aligningcontact pads on a first circuit member with, and electrically couplingto, the distal ends of the compliant members.
 47. The method of claim 41wherein the first circuit member comprises one of a printed circuitboard, a flexible circuit, a bare die device, an integrated circuitdevice, organic or inorganic substrates, or a rigid circuit.
 48. Themethod of claim 41 comprising aligning contact pads on a second circuitmember with the holes in the second carrier, the second circuit memberbeing electrically coupled to the compliant members through the holes inthe second carrier.
 49. The method of claim 48 wherein the secondcircuit member is electrically coupled to the compliant members bysolder.
 50. The method of claim 48 comprising coupling contact pads onthe second circuit member with distal end of a compliant members thatextend through the holes in the second carrier.
 51. The method of claim41 comprising attaching an additional circuitry plane to a second majorsurface of the second carrier, the additional circuitry plane comprisinga plurality of through openings aligned with a plurality throughopenings in the second carrier.
 52. The method of claim 51 wherein theadditional circuitry plane comprises one of a ground plane, a powerplane, or an electrical connection to other circuit members.
 53. Themethod of claim 41 comprising electrically coupling one or more discreteelectrical components to the first flexible circuit member.
 54. Themethod of claim 53 wherein the one or more discrete electricalcomponents comprise capacitors.
 55. The method of claim 41 comprisingthe steps of: positioning a first major surface of a second flexiblecircuit member opposite the first major surface of the second carrier,compliant members on the second flexible circuit member having distalends projecting in openings in the second carrier; and electricallycoupling the compliant members on the first flexible circuit member tothe compliant members on the second flexible circuit member.
 56. Themethod of claim 55 comprising the step of locating a dielectric layerbetween the first and second flexible circuit members.
 57. The method ofclaim 55 comprising selectively soldering compliant members on the firstflexible circuit member to compliant members on the second flexiblecircuit member.
 58. The method of claim 55 comprising selectivelyinserting a conductive member through opposing compliant members on thefirst and second flexible circuit members.
 59. The method of claim 55comprising pressing compliant members on the first flexible circuitmember against opposing compliant members on the second flexible circuitmember.
 60. The method of claim 55 comprising interposing an additionalcircuitry plane between the first and second flexible circuit members.61. The method of claim 60 wherein at least one major surface of theadditional circuitry plane comprises a dielectric layer.
 62. The methodof claim 55 comprising electrically coupling contact pads on a secondcircuit member with distal ends of the compliant members on the secondflexible circuit member.
 63. The method of claim 55 comprisingsingulating the electrical traces on the second flexible circuit memberso that a portion of the compliant members are electrically isolatedfrom the electrical traces.
 64. The method of claim 41 comprisingelectrically coupling a portion of the first flexible circuit memberthat extends beyond the compliant interconnect assembly to anothercircuit member.